Have you ever wondered why coffee beans can be so different? Why is coffee from Ethiopia, for example, often described as “fruity” and coffee from Sumatra "earthy"? It turns out that there are many factors that determine the flavour of the coffee. One determining factor is acidity – how acidic or not a coffee bean is. This article will explore what makes coffee beans more acidic than others and what impact this has on the taste of your favourite cup of coffee!
Is acidity a sensation or a flavour?
Coffee beans can taste acidic because of the presence of acids in coffee. These acids are present naturally and come from coffee cherries, which is why coffee acidity varies between different varieties or cultivars (the type of coffee plant). Coffee isn't overly acidic in and of itself, the pH is actually 4.5 to 6, comparable to peaches, which rates pretty low on the pH scale.
One of the five basic tastes we can perceive on our palates is sourness (along with sweet, bitter, salty, and umami). We actually experience flavour through the combination of taste and fragrance, which is why acidity is frequently a sensation plus a flavor.
What are the acids present in coffee?
The different types of acid present in coffee and their impact on coffee's acidity include: chlorogenic, citric, malic, quinic and caffeic acid which are all found naturally occurring throughout the coffee cherries as well as acetic, formic and lactic. All coffee beans have a combination of these acids, but the concentration and balance is what makes coffee from Ethiopia "fruity" while coffee from Sumatra is described as "earthy".
Coffee acidity varies depending on where it's grown - coffee grown at lower altitudes tastes more acidic because there are fewer buffering agents in coffee cherries.
Citric acid is naturally occurring in coffee and contributes to the sourness of coffee, but it's too faint to be tasted by itself so you can't have a coffee that tastes "citric". Citric acids are also found in lemon juice, orange juice and tonic water. Malic acid on the other hand is more prominent. In fact, if you drink apple cider vinegar for its supposed health benefits your body will actually convert the malic acid into acetic acid which gives it that slightly vinegary taste! This means that coffee from places with high concentrations of apples or grape musts (such as Chile) might exhibit a hint of tartness because there's a higher concentration malic than citric acids.
Caffeic acid is coffee's primary antioxidant which helps to protect coffee from becoming rancid. It can contribute a bitter taste but it doesn't affect coffee's perceived acidity because of its low concentration in coffee cherries. Coffee also contains caffeoylquinic, feruloylquinic and dicaffeoylquinic acids which are all antioxidants.
Quinic acid contributes bitterness to coffee, but it's too faint for us to be able to taste on its own. Instead Italians use quinic acid as a coffee additive because it enhances the flavour of coffee without adding any calories or sugar! The calcium salt of quinic acid is used in some cases as an emulsifier in coffee creamer.
Coffee cherries contain chlorogenic acids too, which are polyphenols that act as antioxidants and antimicrobial agents (which means they help fight off bacteria). Chlorogenic acid breaks down into caffeic and quinic acids which can be bitter tasting at higher levels but it's also important for the body because of its antioxidant properties. It has been shown to have a role in protecting human cells from free radicals, and it can also lower blood pressure.
Roasting coffee and acidity
Acidity diminishes as coffee is roasted. The longer and darker a coffee is roasted acidic compounds are broken down and are overpowered by roasted and bitter notes Beans that have been roasted for less time contain more acids which means they're typically sour or tart tasting.
Coffee turns from green to yellow/light brown during roasting (the coffee roasting process) and the pleasant coffee flavour we know comes from a combination of sugars, amino acids, proteins and lipids. These compounds are created by thermal degradation - basically they're caused by heat which breaks down carbon bonds in chemicals that make up coffee beans through various chemical reactions (e.g., pyrolysis).
Influencing acidity after roasting
You can control your coffee acidity during brewing - to a certain degree. There are coffee brewing techniques that will help you to enhance acidity and there are coffee brewing techniques which make coffee less acidic.
When making coffee, acids are extracted first and sugars afterward. If your cup is excessively acidic, you may slow down the brewing process by using a finer grind to release more sugar for a sweeter taste. You can speed up the brewing process by increasing the coarseness of ground coffee if it tastes flat.
Tweaking the water temperature can also help you adjust acidity. Higher water temperatures extract acids easier than lower temperatures.
Coffees that display acidityLooking for coffees with an acidic side? Start with these recommendations from our online coffee store.
Fazenda Joia Rara packs a lot of tropical fruit notes and carries delicious acidic notes. This fermented coffee performs in all brewing methods, but reveals its acidic side specially as a pour-over.
Fazenda Cachoeira has a crisp and clean orange acidity that mingles with cocoa for a deeply satisfying cup.
La Guadalupana is a nicaraguan coffee that bursts with nutty, floral tasting notes, it is creamy, has medium acidity, and long aftertaste.